6. (Anat.) Lying toward the mesial plane; mesial. {Internal angle} (Geom.), an interior angle. See under {Interior}. {Internal gear} (Mach.), a gear in which the teeth project inward from the rim instead of outward. Syn: Inner; interior; inward; inland; inside.
internal angle n : the angle inside two adjacent sides of a polygon [syn: {interior angle}]